Common Misconceptions in Haloalkanes & Haloarenes

Statement	True/False	Correction
"SN2 gives a racemic mixture"	FALSE	SN2 gives complete Walden inversion (one enantiomer only, opposite to starting material). Racemization is the outcome of SN1.
"SN1 gives inversion because the nucleophile attacks the weaker side"	FALSE	SN1 gives RACEMIZATION. The planar carbocation is attacked from both faces equally → 50:50 R:S mixture.
"The C-Cl bond in chlorobenzene is WEAKER than in chloroethane"	FALSE	The C-Cl bond in chlorobenzene is STRONGER and SHORTER (169 pm vs 177 pm) due to partial double bond character from p-π resonance.
"C-F is the most reactive because C-F is the shortest bond"	FALSE	C-F is the LEAST reactive because C-F is the strongest bond $\frac{485 kJ}{mol}$ and F- is the worst leaving group. Shortest = strongest, not weakest.
"C-I is the least reactive because C-I is the weakest/longest bond"	FALSE	C-I is the MOST reactive. The weak/long C-I bond breaks easily, and I- is the best leaving group. Weakest bond = most reactive.
"Tertiary substrates undergo SN2 readily because they have stable carbocations (good for SN1)"	FALSE	Tertiary substrates undergo SN1 (stable carbocation = good for SN1), but CANNOT undergo SN2 (three bulky groups block backside attack). These are separate mechanistic considerations.
"Primary substrates always undergo SN1 in polar protic solvent"	FALSE	Primary substrates do NOT undergo SN1 regardless of solvent — primary carbocations are too unstable. Primary substrates prefer SN2 (or E2 with strong bulky base).
"DMSO (polar aprotic) favors SN1 because it is polar"	FALSE	DMSO favors SN2 by leaving the nucleophile unsolvated. Polar protic solvents (water, ethanol) favor SN1 by stabilizing the carbocation intermediate.
"Aqueous KOH and alcoholic KOH give the same products"	FALSE	Aqueous KOH → SN2 substitution (haloalkane → alcohol). Alcoholic KOH → E2 elimination (haloalkane → alkene). The solvent determines the product.
"The Finkelstein reaction uses KI (potassium iodide)"	FALSE	The Finkelstein reaction specifically uses NaI (sodium iodide). NaI is soluble in acetone; NaCl is not — this solubility difference is the driving force. KI has different solubility properties.
"DDT depletes the ozone layer"	FALSE	CFCs (chlorofluorocarbons) deplete the ozone layer. DDT causes environmental harm through biomagnification in food chains (not ozone depletion).
"CFCs bioaccumulate in fatty tissues like DDT"	FALSE	CFCs are volatile — they escape to the stratosphere. DDT bioaccumulates in fat because it is a heavy, lipophilic solid. They have different environmental fates.
"Grignard reagents can be prepared in water or ethanol"	FALSE	Grignard reagents are immediately destroyed by water or alcohols (R-MgX + $H_{2}O$ → R-H + Mg(OH)X). Only dry, anhydrous ether or THF can be used.
"Saytzeff's rule always applies in elimination"	FALSE	Saytzeff's rule applies for E1 and E2 with non-bulky bases. With a very bulky base (tert-butoxide), Hofmann's rule applies — the LESS substituted alkene is the major product (steric control overrides thermodynamic preference).
"Carbocation rearrangement can occur in SN2"	FALSE	Carbocation rearrangement requires a discrete carbocation intermediate, which only exists in SN1 and E1. SN2 is a single-step concerted reaction — there is no intermediate, so rearrangement is impossible.
"The Dow process is SN2 substitution"	FALSE	The Dow process is Nucleophilic Aromatic Substitution (NAS), not SN2. The mechanism is addition-elimination (via Meisenheimer complex), not backside attack on sp3 carbon.
"Rate of SN1 increases when concentration of nucleophile is increased"	FALSE	Rate of SN1 = k[RX] — it is ZERO-order in nucleophile concentration. Doubling [Nu] has absolutely no effect on the SN1 rate.